This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This project examines the behavioral and physiological consequences of the loss of a bonded partner in monogamous prairie voles. Male prairie voles bond with their mate through mechanisms involving vasopressin and dopamine. However little is known about the consequences of social loss. In the past year we have found that loss of a partner (but not of a sibling) results in an increase in basal stress hormones as well as passive behavior in the forced swim test and tail suspension test. These changes are reminiscent of the behavioral changes associated with depression. We hypothesized that the peptide CRF might be involved in these behavioral changes. Indeed we found that blocking CRF receptors at the time of losing the partner completely blocks the emergence of depressive-like behavior. These studies provide an important animal model for understanding the consequences of social loss, grieving, and depression.